The continuing progress in the delivery of high-definition digital video to the consumer has brought with it new challenges in the protection of intellectual property rights. In earlier days, the digital content of a Digital Video Disk (DVD) movie was converted to an analog signal (played) on a DVD player that connected to a television by analog cables. If a would-be counterfeiter copied the analog signal to a new DVD, the analog degradation of the signal made for a reduced quality copy that was inferior to the original DVD. Copyright holders were somewhat comfortable with the competitive advantage that the quality difference gave them.
With the advent of very-high-resolution digital displays and the digital/digital conversion of content that feeds them, the ability of counterfeiters to produce high-quality copies of DVD movies, for example, is greatly enhanced. A Digital Video Interface (DVI) or High-Definition Multimedia Interface (HDMI) stream can be copied to a new DVD that can be an exact replica of the original. Copyright infringement can go undetected and copyright owners can find themselves holding property whose value is degraded.
A number of methods and devices have been developed to prevent illicit copying of digital content. One of these is High-bandwidth Digital Content Protection (HDCP). HDCP is a protocol designed for protecting audio-visual content over certain high-bandwidth interfaces, referred to as HDCP-protected Interfaces. HDCP-protected Interfaces include Digital Video Interface (DVI), High Definition Multimedia Interface (HDMI), and the onboard exchange of protected digital content within such open source platforms as personal computers.
In an HDCP System, two or more HDCP Devices are interconnected through an HDCP-protected Interface. The Audio-visual Content protected by HDCP, referred to as HDCP Content, flows from the Upstream Content Control Function into the HDCP System at the most upstream HDCP Transmitter. From there, the HDCP Content, encrypted by the HDCP System, flows to HDCP Receivers over HDCP-protected Interfaces.
HDCP Receivers decrypt the HDCP Content to audio and video suitable for human viewing. HDCP Receivers can also be HDCP Repeaters that serve as downstream HDCP Transmitters emitting the HDCP Content further downstream to additional HDCP Receivers.
HDCP uses an array of public and private digital keys to effect its protection. An HDCP device, such as a DVD player or a high-resolution monitor, is given a set of 40 fifty-six-bit private keys and a key-selection vector (KSV) at manufacture. The keys and KSV are assigned and validated by DCP and are stored in the HDCP appliance, typically in an EEPROM, flash memory device, or other long-term memory. The private cryptographic keys are typically stored in logically sequential storage locations, such as rows and columns or word-lines and bit-lines, with each row including an entire key. If a would-be counterfeiter, even if a legitimate purchaser, were to remove and read the EEPROM or other device on which the private keys are stored, the legitimate keys can be replicated and used in a non-legitimate device. In addition, when the keys and KSV are given to a contract manufacturer for storage in a specific product, there is the possibility that the keys and KSV can be used for non-authorized products.
Thus, there is a need for a method and apparatus that will protect private cryptographic keys from illegitimate copying and piracy. Such a method and apparatus must allow full compatibility and operability in the digital content protection environment.